# Patent

## Title
Process of manufacturing a magnetic write head

## Abstract

One of the major requirements for higher frequency extendability is to reduce yoke length and inductance in order to have fast saturation. This has been accomplished by using a design that provides a cavity in the lower pole piece inside which is located at least two coils, one on top of the other. A process for manufacturing the device is also described.

## Background
FIELD OF THE INVENTION
The invention relates to the general field of magnetic write heads for data storage systems with particular reference to increasing the writing speed.
BACKGROUND OF THE INVENTION
There are several design options available to make high data rate writers. One of the major requirements for higher frequency extendability is to reduce yoke length and inductance in order to have fast saturation. Given fast saturation during the writing process, one can have better overwrite and cold overwrite performance at higher frequency. Some designs for faster write heads have the planar writer with a short yoke length. However, one of the drawbacks of this design is the coil real estate utilization which creates either high DC coil resistance or requires a small number of coil turns.
In FIG. 1 we show a typical write head of the prior art. Seen there is magnetic shield 11 which is separated from the lower magnetic pole by insulating layer 12. The lower pole is made up of two parts—base 13 and upper portion 14 which is open so that it forms a cavity. In this cavity is housed magnetic coil 16 which is seated on shallow pedestal 15. Insulating layers 17 and 18 cover the coil while insulating layer 19 serves to control throat height (see later). Non-magnetic gap layer 20 separates the lower coil structure from upper pole 21.
A routine search of the prior art was performed with the following references of interest being found:
In U.S. Pat. No. 6,325,947 B1, Garfunkel et al. show a process for a head with a short yoke while Nakajima et al. show a process for a head in U.S. Pat. No. 6,317,280 B1. Santini shows a process for a head in U.S. Pat. No. 6,339,523 B1 and related patents are U.S. Pat. No. 6,333,830 B2 (Rose et al.) and U.S. Pat. No. 6,304,414 B1 (Crue, Jr. et al.).
SUMMARY OF THE INVENTION
It has been an object of at least one embodiment of the present invention to provide a magnetic write head having fast saturation.
Another object of at least one embodiment of the present invention has been that said write head occupy minimum real estate and have minimum electrical resistance.
Still another object of at least one embodiment of the present invention has been to provide a process for manufacturing said write head.
These objects have been achieved by forming a cavity in the lower pole piece and locating therein at least two coils, one on top of the other. A process for manufacturing the device is also described.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a typical write head of the prior art FIG. 2 shows the starting point for the process of the present invention.
FIGS. 3-5 show steps leading to the formation of the lower coil and the cavity in which it is housed.
FIG. 6 is a plan view of the cross-sectional view seen in FIG. 5.
FIGS. 7-8 show steps leading to the formation of the upper coil and the cavity in which it is housed
FIG. 9 shows the step for controlling the throat height of the device.
FIG. 10 shows the addition of the non-magnetic gap layer.
FIG. 11 shows the completed device.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is based on a two layer coil structure for a planar writer. This two layer structure design leads to low DC coil resistance relative to similar designs having a short yoke.
A key feature is breaking the lower pole into two separate layers which allows the achievement of an optimized coil space for each coil. This two layer coil structure enables one to maintain the same planar writer structure but with better performance on fast saturation and lower DC coil resistance or better thermal pole tip protrusion.
The process of the present invention begins, as shown in FIG. 2, with the deposition of layer 11 which will serve as the lower magnetic shield. It is between about 1 and 2 microns thick and is of a metal such as NiFe or CoNiFe. This is followed by layer 12, between about 1,000 and 5,000 Angstroms thick, made of alumina, whose purpose is to separate the reader shield and the writer's bottom pole. Then, layer 13 (of the writer's bottom pole) is deposited onto layer 12 to a thickness between about 1 and 2 microns. It will serve as the lower magnetic pole of the writer.
Referring now to FIG. 3, insulating layer 15 (of alumina or silica), between about 1,000 and 3,000 Angstroms thick, is deposited onto layer 13 and patterned to form a low pedestal. This is followed by the deposition of a seed layer, typically of copper, (not shown) which, after protection of the appropriate areas by photoresist (also not shown), is used as a base onto which to electrodeposit lower coil 16. After removal of both the photoresist and the unplated portions of the seed layer, the structure is as seen in FIG. 3.
Next, as shown in FIG. 4, the bottom section 14 of the lower pole is formed by electroplating. Insulating layer 17 is then formed of photoresist to a thickness that is between a 6,000 and 10,000 Angstroms, and then selectively removed from above 14, giving the structure the appearance seen in FIG. 4. Layer 17 is then hard baked to become a permanent insulating layer.
The next step is the overfilhing of the space above layer 17 with insulating layer 58 (alumina between about 1,000 and 5,000 Angstroms thick) following which the structure is planarized (typically using CMP) so that the thickness of the bottom section of the lower pole (now shown as layer 24) is reduced, as can be seen in FIG. 5. The deposition is performed in two separate layers is to avoid void formation in layer 58.
FIG. 6 is a plan view of the structure whose cross-section we saw in FIG. 5.
The process continues with the formation of upper coil 76 which is formed on the surface of layer 58 in a similar manner to that described above for lower coil 16. Layers 76, 87 and 88 are formed using similar materials and thicknesses to layers 16, 17 and 58 respectively as shown in FIG. 7. In a similar manner to the earlier formation of layer 24, layer 74 (the top section of the lower pole) is also formed. This is followed, as before, by a planarization step whereby layer 74 is reduced in thickness, being now designated as 84 in FIG. 8. Thus, layers 24 and 64 together constitute the lower pole, for a total thickness between about 0.6 and 1.5 microns. being functionally equivalent to layer 14 in FIG. 1.
Referring next to FIG. 9, a shallow trench, between about 2000 and 4,000 Angstroms deep, is etched into layer 88 as well as a small portion of the lower pole on one side of the structure only. This cavity is then overfilled with material 91 (such as alumina or silica about 1,000 to 5,000 Angstroms thick) and the structure is then planarized, as shown in FIG. 9 until some of layer 84 begins to be removed. As a result, width 92 of the lower pole, on one side, is gradually decreased so that the throat height of the finished structure can be controlled to be between about 0.6 and 1.2 microns.
FIG. 10 shows the structure after the deposition of write gap layer 20. In principle this could be any non-magnetic material but our preferred material for layer 20 has been ruthenium or rhodium, deposited to a thickness between about 7,000 and 10,000 Angstroms. Note that layer 20 has been selectively removed from the one side of lower pole 84 to form a flux transmission area that will allows unimpeded passage of magnetic flux between the upper and lower magnetic poles.
The process of the present invention concludes with the successive depositions of layers 110 and 112, as illustrated in FIG. 11. Layer 110 is between about 1,000 and 6,000 Angstroms thick and is made of a material capable of sustaining a very high magnetic moment. Examples are CoFeN and CoFe, with CoFeN being preferred. The magnetic permeability of layer 110 was generally between about 700 and 1,000. The presence of layer 110 right above write gap 20 ensures a concentration of magnetic flux in the immediate vicinity of the latter. Layer 112 is of the same material as layers 13, 24, and 84 and serves as the upper magnetic pole. It is between about 1 and 1.5 microns thick.

## Claims

1. A process to manufacture a magnetic write head, having a lower pole, comprising:
on a substrate, depositing a shield layer, then depositing a first insulating layer on said shield layer and then depositing a lower magnetic pole layer, having a thickness and an upper surface, on said first insulating layer; 
on said lower magnetic pole layer, depositing a second insulating layer, patterned to have the form of a low pedestal surrounded by an area of said upper surface; 
on said pedestal, forming a first conductive seed layer which is masked by first photoresist so as to expose an area having the shape of a lower coil; 
then electroplating conductive material onto all unmasked areas of said seed layer, thereby forming, after removal of said first photoresist and all unplated seed areas, the lower coil on said pedestal; 
after protecting said lower coil and said pedestal with second photoresist, forming a bottom section of said lower pole, through electroplating, to a first maximum thickness, thereby forming a first cavity which houses said lower coil; 
then hard baking said second photoresist whereby said second photoresist becomes a third insulating layer; 
overfilling said first cavity with a fourth insulating layer and then planarizing until said first maximum thickness of the lower pole has been reduced; 
on said fourth insulating layer, forming a second conductive seed layer which is masked by third photoresist so as to expose an area having the shape of an upper coil; 
then electroplating conductive material onto all unmasked areas of said second seed layer, thereby forming, after removal of said third photoresist and all unplated seed areas, the upper coil on said fourth insulating layer; 
after protecting said upper coil and said fourth insulating layer with fourth photoresist, forming a top section on said bottom lower pole section to a second maximum thickness through electroplating, thereby forming a second cavity that houses both coils; 
then hard baking said fourth photoresist whereby said fourth photoresist becomes a fifth insulating layer; 
overfilling said second cavity with a sixth insulating layer and then planarizing until said second maximum thickness of the lower pole has been reduced; 
etching a shallow trench, having sloping sides, in said sixth insulating layer as well as in a portion of said lower pole, on one side only, and then overfilling said shallow trench with a seventh insulating layer; 
planarizing said lower pole and said seventh insulating layer until an amount of said lower pole is removed, thereby determining throat height for said write head; 
depositing a non-magnetic gap layer on said seventh insulating layer and on all of said lower magnetic pole except for a flux transmission area that extends across a portion of said lower pole, being located across said second cavity from said one side; 
depositing a layer of a high magnetic moment material on said gap layer and on said flux transmission area; and 
on said high magnetic moment layer, depositing an upoer pole layer, thereby forming an upper magnetic pole.

2. The process described in claim 1 wherein said first insulating layer is alumina and is deposited to thickness between about 1,000 and 3,000 Angstroms.

3. The process described in claim 1 wherein said second insulating layer is alumina and is deposited to thickness between about 1,000 and 3,000 Angstroms.

4. The process described in claim 1 wherein, after baking, said third insulating layer has a thickness between about 6,000 and 10,000 Argstroms.

5. The process described in claim 1 wherein said fourth insulating layer is alumina and is deposited to thickness between about 1,000 and 5,000 Angstroms.

6. The process described in claim 1 wherein said fifth insulating layer, after baking, has a thickness between about 6,000 and 10,000 Angstroms.

7. The process described in claim 1 wherein said sixth insulating layer is alumina and is deposited to thickness between about 1,000 and 5,000 Angstroms.

8. The process described in claim 1 wherein said seventh insulating layer is alumina and is deposited to thickness between about 4,000 and 5,000 Angstroms.

9. The process described in claim 1 wherein said non-magnetic gap layer is ruthenium or rhodium and is deposited to thickness between about 7,000 and 10,000 Angstroms.

10. The process described in claim 1 wherein said high magnetic moment material is CoFeN.

11. The process described in claim 1 wherein said high magnetic moment material is deposited to thickness between about 1,000 and 6,000 Angstroms.

12. The process described in claim 1 the step of planarizing said lower pole and said seventh insulating layer results in a throat height that is between about 0.6 and 1.2 microns.

13. The process described in claim 1 wherein each coil has at least 4 turns.

14. The process described in claim 1 wherein said lower magnetic pole is deposited to a thickness between about 0.6 and 1.5 microns.